Children born to women poisoned by PCB-contaminated cooking oil were smaller and had more physical and mental problems than other children, researchers said.

In 1979, at least 2,000 people in Taiwan were poisoned by cooking oil laden with the toxic chemical polychlorinated biphenyls, or PCBs. Heating of the oil caused some of the PCBs to be converted into a chemical called polychlorinated dibenzofurans, which are believed to be even more toxic. The oil was pulled from the market in October 1979, about 10 months after the first cases of "oil disease" were reported.A team of U.S. and Taiwanese researchers conducted a field survey in 1985 of all living children born to women who had consumed the contaminated oil. The only means by which the children, some of whom were born years after their mothers consumed the contaminated oil, could have come in contact with the PCBs was through "transplacental exposure and possibly exposure through breast milk," said the researchers, who published their findings in the journal Science.

"The syndrome is one of the very few documented to result from transplacental exposure to pollutant chemicals," the researchers said. The placenta, a blood-rich structure that delivers oxygen and nutrients to the fetus, acts as a barrier to most chemicals.

The survey found the 128 exposed children, whose average age was 32 months, were smaller than a control group of youngsters whose mothers who did not consume contaminated oil. The exposed children weighed 7 percent less and were about 3 percent shorter on average than those not exposed.

Nail and tooth deformities, abnormally darkened skin and eyelid swelling were more common in the exposed children, who also had a substantially higher incidence of bronchitis.

The mental development of such children also appeared to be impaired, as reflected by lower scores on three tests of mental development and skill. Verbal IQ scores were similar to those of unexposed children.

The scientists said the PCB exposure in the uterus appeared to produce a "general disorder of ectodermal tissue," - parts of the body like the nervous system, eyes, ears, fingernails, hair, skin glands and some mucous membranes - that develop from the outer layers of the earliest stages of an embryo.